See, for questions like this, I'd try http://forums.digitalspy.co.uk/ for no other reason than it's a huge forum with very active general discussion and advice forums. It's where I go for all my Big Brother flame wars, but it's also full of civilized discourse.

Post a query like, "Advice on architectural term" and there will be a dozen architects reading it.

You can't post pictures directly in the forum though, so you'd need to link to it. (edit: weird - I was sure you posted a picture.)

Couldn't it be a Mews as well? Wikipedia mentions that it can be and if the space is as you describe I'd think Mews would fit even though it's not a stable or other such space, just due to the fact it is a passageway.

Here in the UK, I do not believe that such a passageway would ever be called a Mews.

I agree that passageway seems most appropriate. We use "jitty" here in the Midlands, but in our case it refers to a narrow unpaved lane, so there could be confusion in the wider world if you called it that.